A projection exposure apparatus configured to expose a circuit pattern of a reticle (mask) onto a wafer via a projection optical system has conventionally been known, and a high resolution exposure apparatus is increasingly required.
An immersion exposure calls attentions as one measure to meet the demand for the high resolution. The immersion exposure further promote an increase of a numerical aperture (“NA”) of a projection optical system by using a liquid (immersion liquid) as a medium at the wafer side of the projection optical system. Since the NA of the projection optical system is defined as NA=n×sin θ where n is a refractive index of the medium, NA can be increased up to n by using a medium having a refractive index higher than that of air (n>1) between the projection optical system and the wafer. By so doing, the resolution R of the exposure apparatus, which is expressed as R=k1×(λ/NA) with a wavelength λ of a light source and a process constant k1.
In the immersion exposure, a local fill system that locally fills a liquid in a space between the final surface and the wafer is proposed (see, for example, a Patent Document 1).
Patent Document 1: Japanese Domestic Publication No. 2004-086470.